[Fix] Could Not Connect to One or More vCenter Server Systems

Case: could not connect to one or more vCenter Server systems

vCenter Server is the centralized management utility for VMware, and is used to manage multiple ESXi hosts, virtual machines, and all dependent components from a single centralized location. If you need to manage a large virtual environment, you can register multiple vCenter Servers against a single SSO server by enabling Enhanced Linked Mode (ELM).

However, sometimes when using Enhanced Linked Mode, the VMware vSphere web client may display the error:

• Failed to verify the SSL certificate for one or more vCenter Server Systems: https://vCenterServerFQDN:443/sdk
• Could not connect to one or more vCenter Server Systems: https://vCenterFQDN:443/sdk

And objects such as host or virtual machines are not displayed in the vSphere Web Client. So, what causes it and how to fix this error? This article will answer it for you.

Causes of “Could not connect to one or more vCenter Server systems” error

If you got the VMware vCenter error “could not connect to one or more vCenter Server systems”, and find yourself cannot connect to vCenter Single Sign-On (SSO), first you need to identify what reason is causing this error from happening.

According to VMware, this issue occurs in these situations when using Enhanced Linked Mode:

• Another vCenter Server in the Single Sign-On (SSO) domain has restarted or is not fully available following a restart.
• During the re-installation of vCenter Server, it is possible to have the same vCenter Server registered more than once to Single Sign-On (SSO).
• With a previous install of vCenter Server, SSL certificates are not overwritten or removed properly during an upgrade or re-installation.

How to fix “Could not connect to one or more vCenter Server systems”

This section will present you several resolutions to the VMware vCenter error “could not connect to one or more vCenter Server systems”. But before that, please note that when a vCenter Single Sign-On service error occurred, first you need to troubleshoot simple causes, such as checking if invalid vCenter Single Sign-On credentials are being used, or waiting 10 minutes, log out and log back in to the vCenter Server, to see if the error clear on its own.

This is because the error may be transient as another vCenter Server in an Enhanced Link Mode domain is restarting. If all vCenter Servers are up and running and this error persists, then you can continue with this resolution to identify duplicate service registrations or other errors.

Find and unregister a duplicate registered vCenter Server instance

1. Log in to the server with the Platform Services Controller installed.

2. Open a Windows Command Prompt as administrator, and run the following command to create a text file with a list of the services registered within the Platform Services Controller.

"%VMWARE_PYTHON_BIN%" "%VMWARE_CIS_HOME%\VMware Identity Services\lstool\scripts\lstool.py" list --url http://localhost:7080/lookupservice/sdk --type vcenterserver > c:\psc_services.txt

3. Open the generated text file to find a list of services registered to the Platform Services Controller.

In the text file, you see output similar to:

Name: AboutInfo.vpx.name
Description: AboutInfo.vpx.name
Service Product: com.vmware.cis
Service Type: vcenterserver
Service ID: 608AF497-B198-40D1-9855-545533A488AF
Site ID: home-office
Node ID: 86ca3bf1-9201-11e3-8f19-000c29562ae2
Owner ID: [email protected]
Version: 6.0
Endpoints:
Type: com.vmware.cis.workflow
Protocol: vmomi
URL: http://vCenter1.domain.local:8088
SSL trust:
 
Name: AboutInfo.vpx.name
Description: AboutInfo.vpx.name
Service Product: com.vmware.cis
Service Type: vcenterserver
Service ID: 6ae3bf1a-9318-4a33-b2cb-d2eaa7a306c5
Site ID: home-office
Node ID: 86ca3bf1-9201-11e3-8f19-000c29562ae2
Owner ID: [email protected]
Version: 6.0
Endpoints:
Type: com.vmware.cis.workflow
Protocol: vmomi
URL: http://vCenter2.domain.local:8088
SSL trust:
 
Name: vCenterService
Description: vCenter Server
Service Product: com.vmware.cis
Service Type: vcenterserver
Service ID: default-first-site:01c98f18-770a-41c2-a967-b7a4b574cad2
Site ID: default-first-site
Owner ID: [email protected]
Version: 5.5
Endpoints:
Type: com.vmware.vim
Protocol: vmomi
URL: https://Legacy_vCenter.domain.local:443/sdk

4. Unregister a duplicate vCenter Server service. run the following command to unregister the duplicate service endpoint.

"%VMWARE_PYTHON_BIN%" "%VMWARE_CIS_HOME%\VMware Identity Services\lstool\scripts\lstool.py" unregister --url http://localhost:7080/lookupservice/sdk --id Service_ID from Step 4 --user "[email protected]l" --password "administrator_password" --no-check-cert

For example:

"%VMWARE_PYTHON_BIN%" "%VMWARE_CIS_HOME%\VMware Identity Services\lstool\scripts\lstool.py" unregister --url http://localhost:7080/lookupservice/sdk --id 608AF497-B198-40D1-9855-545533A488AF --user "[email protected]" --password "VMware123!" --no-check-cert

Re-install VMware products

If unregister the duplicate vCenter Server instance cannot resolve the issue that you cannot connect to vCenter Single Sign-On, you may need to re-install the VMware products.

1. Unregister vCenter Server and its components according to the advised order is:

• vSphere web client
• vCenter Server
• vCenter Inventory Service
• vCenter Single Sign-On

2. Remove the RSA database the RSA_USER and RSA_DBA users.

3. Rename these folders containing SSL information:

• Rename C:\Program Files\VMware\Infrastructure to InfrastructureOld
• Rename C:\ProgramData\VMware\Infrastructure to InfrastructureOld
• Rename C:\ProgramData\VMware\VMware VirtualCenter to vCenterOld
• Rename C:\ProgramData\VMware\vSphere Web Client to WebClientOld
• Rename C:\ProgramData\VMware\SSL to SSLOld

4. Create a new RSA database and users using the provided scripts. Create the RSA_USER and RSA_DBA users using the script named rsaIMSLiteMSSQLSetupUsers.sql, which is included on the vCenter Server install media.

5. Install vCenter Server and its components in this order:

• SSO
• Inventory Service
• vCenter Server
• vSphere web client

6. Log in to vCenter Server via the Web Client and verify that the issue is resolved.

VM data protection: batch backup VMs on vCenter Server

vCenter Server is a very convenient official platform for centrally managing multiple ESXi virtual machines, patches, and automate ESXi host configuration, etc. However, it does not provide the feature of virtual machine backup. Therefore, you cannot try VMware vCenter backup virtual machine. And that makes backup software the commonly accepted choice to protect VM data, and by far the most convenient.

Here I introduce you to a VMware backup software AOMEI Cyber Backup, it enables you to backup multiple VMs in 3 simple steps. And it offers you the following benefits

✦ Agentless Backup: create complete and independent image-level backup for VMware ESXi and Hyper-V VMs.
✦ Flexible vSphere Backup: batch backup large numbers of VMs managed by vCenter Server, or multiple VMs on a standalone ESXi host.
✦ Multiple Storage Destinations: backup to local drive, or network destinations like Windows share or NAS.
✦ Automated Execution: create backup schedules to automate backups daily, weekly, and monthly with email notifications.
✦ Role Assignment: allows one administrator to create sub-accounts with limited privileges.

AOMEI Cyber Backup supports VMware ESXi 6.0 and later versions. Next, I will show you how to perform vSphere backup and restore via AOMEI Cyber Backup. You can click the following button to download the 30-day free trial.

*You can choose to install this VM backup software on either Windows or Linux system.

4 Steps to batch backup VMs on vCenter Server

1. Bind Devices: Access to AOMEI Cyber Backup web client, navigate to Source Device > VMware > + Add VMware Device to Add vCenter or Standalone ESXi host. And then click … > Bind Device.

2. Create Backup Task: Navigate to Backup Task > + Create New Task, and then set Task Name, Backup Type, Device, Target, and Schedule.

• Task Name: you can change the task name or use the default name with an ordinal.
• Device: batch select large numbers of VMs managed by vCenter Server for centralized backup.

• Target: select to back up to a local path, or to a network path.
• Schedule (optional): perform full, differential, or incremental backup, and automate execution according to the frequency you specified.

• Cleanup (optional): automatically delete the old backup copies that exceed the retention period you specified.

3. Run Backup: Click Start Backup and select Add the schedule and start backup now, or Add the schedule only.

Created backup tasks will be listed and monitored separately, for restoring, progress checking and schedule changing.

When restoring, you can also restore to new location to create a new VM in the same or another datastore/host directly from the backup, saving the trouble of re-configuring the new VM.

Summary

By enabling Enhanced Linked Mode, you can register multiple vCenter Server against a single SSO server. However, it may also cause a vCenter Single Sign-On service error occurred. This article presented 2 ways to resolve the VMware vCenter error “could not connect to one or more vCenter Server systems”.

If you are concerned that errors may lead to unexpected data loss, performing regular backups is an effective way to save you from this situation. You can try AOMEI Cyber Backup, a VMware backup software that enables you to create backup tasks cover multiple VMs, and automate the VM protection.